1. Field of the Invention
The present invention relates to filters for cigarettes, and more particularly to a filter device for a cigarette which includes a porous filter rod and an impermeable mouthpiece having smoke flow passages therethrough for delivering filtered and ventilated smoke to the smoker's mouth.
2. Description of the Prior Art
It is known in the art to add filters to cigarettes wherein the filters are provided with ventilation means to bring ambient air into the filter to dilute the smoke stream passing therethrough. The dilution of the smoke stream reduces the quantity of smoke particles as well as the gas phase components which are delivered to the smoker's mouth. A number of means have been proposed and are utilized for introducing ventilating air into the cigarette. For example, the wrapper for the tobacco column of a cigarette can be made from a porous material which allows for the introduction of air along the entire length of the tobacco column where it mixes with the smoke stream passing therethrough thereby diluting the smoke in the stream. Also, the cigarette wrapper may be perforated at selected locations along the tobacco column to provide ports in the tobacco column through which ventilating air enters. Even further, it is known to perforate the wrapper or tipping material of the filter at the end of a tobacco column to allow ventilating air to enter the filter and dilute the smoke stream as it is being filtered.
Devices for diluting smoke with ventilating air before the smoke is filtered are also known. One example of such a device is shown in U.S. Pat. No. 3,552,399. The device, therein referred to as a filter for homogenizing air and smoke has a blind ended, longitudinal, central axial passageway. In one embodiment of the filter, the central axial passageway is open to a filter element. A plurality of longitudinal passageways surround and extend parallel to the central passageway, and transverse passageways interconnect the longitudinal passageways and central passageway with each other and with the ambient. As the cigarette to which the device is attached is smoked, smoke and ambient air traverses the longitudinal and central passageways wherein the smoke and air are mixed before being filtered by the filter element.
Devices are also known for delivering unfiltered smoke and ventilating air to the smoker's mouth. For example, U.S. Pat No. 4,023,576 shows a cigarette with a hollow mouthpiece which defines a smoke chamber. The smoke chamber is separated from the tobacco column by two spaced apart baffle plates which define a curved path which the smoke must traverse before entering the smoke chamber. The mouth end of the chamber is closed by a wall having a central orifice for the flow of smoke out of the smoke chamber into the smoker's mouth. The exterior surface of the mouthpiece is provided with longitudinal grooves which cooperate with an overlaying perforated tipping paper to define flow paths for ventilating air. When a smoker draws on the mouthpiece, undiluted, unfiltered smoke is drawn from the tobacco column into the smoke chamber and through the outlet orifice centrally of the mouthpiece and into the smoker's mouth. At the same time, ventilating air is drawn in through the tipping paper and longitudinal grooves to mix with the undiluted smoke within the smoker's mouth.